Idea Transcript
ESTABLISHING OCCUPATIONAL EXPOSURE LIMITS IN YOUR WORKPLACE
Protecting All Workers
Funded By Workers Compensation Board of Manitoba Community Initiatives and Research Program
ESTABLISHING OCCUPATIONAL EXPOSURE LIMITS IN YOUR WORKPLACE
Published by
OHG Consulting Inc. 108 Turnbull Dr. Winnipeg MB R3V 1X2 ohgconsulting.com 204-261-1770
Project Coordinator
John Elias, MPH, CIH, ROH, CRSP
Project Funding
Workers Compensation Board of Manitoba Community Initiatives and Research Program
TABLE OF CONTENTS ESTABLISHING OCCUPATIONAL EXPOSURE LIMITS IN YOUR WORKPLACE ........ 0 TABLE OF CONTENTS .................................................................................................. 2 DEFINITIONS ................................................................................................................. 3 INTRODUCTION TO THE GUIDELINE .......................................................................... 5 What Are Our Responsibilities For Workers’ Health? .................................................. 5 General Duties ......................................................................................................... 5 Exposure To Chemical Substances ......................................................................... 5 What Are Occupational Exposure Limits And Why Must They Be Adjusted? .............. 7 What Is The Purpose of This Guideline? ..................................................................... 7 What Are The Principles Used In This Guideline? ....................................................... 8 ADJUSTMENTS FOR CONDITIONS OF THE WORKER............................................... 9 INTRODUCTION - WORKER ....................................................................................... 10 CAUTIONARY NOTES ................................................................................................. 11 ADJUSTMENTS FOR AGE ........................................................................................... 12 ADJUSTMENTS FOR HEALTH .................................................................................... 15 ADJUSTMENTS FOR SEXUAL DIFFERENCES .......................................................... 18 ADJUSTMENTS FOR PREGNANT WORKERS............................................................ 19 ADJUSTMENTS FOR SENSITIZATION ....................................................................... 23 ADJUSTMENTS FOR NONOCCUPATIONAL EXPOSURES ....................................... 25 ADJUSTMENTS FOR CONDITIONS OF THE WORKPLACE ...................................... 26 INTRODUCTION - WORKPLACE ................................................................................. 27 ADJUSTMENTS FOR UNUSUAL WORK SCHEDULES .............................................. 28 ADJUSTMENTS FOR MULTIPLE ROUTES OF EXPOSURE ...................................... 33 ADJUSTMENTS FOR EXPOSURE TO MULTIPLE CHEMICALS ................................ 35 ADJUSTMENTS FOR PHYSICAL EXERTION ............................................................. 38 ADJUSTMENTS FOR UNUSUAL TEMPERATURES ................................................... 41
2
DEFINITIONS ACGIH® \BEIs® Biological half-life Biotransformation
Body Burden C/B Documentation Dose Metabolism Occupational Physician
Occupational Exposure Limit OEL Potentiating
ppm
Skin Notation
Synergistic effect TLVs® TLV-STEL TLV-TWA
American Conference of Governmental Industrial Hygienists – The association that establishes the TLVs. Biological Exposure Indices – guidance values for assessing biological monitoring results. The time required for the body to eliminate one-half of an administered dose. Biotransformation is the process whereby a substance is changed from one chemical to another (transformed) by a chemical reaction within the body. Metabolism or metabolic transformations are terms frequently used for the biotransformation process. The total amount of a substance in the body following exposure. Chemical or biological substance. A publication by ACGIH that contains supporting data and rationale for the TLVs. The amount of a substance to which a worker is exposed. The transformation of energy and matter within the body. A physician having the professional training, skills and competence to advise on the clinical management of people at work and upon the impact of environmental factors facing the general community. The limit of exposure of a worker to an airborne chemical or biological substance established under Part 36 of the Manitoba Workplace Safety and Health Regulation. Occupational Exposure Limit One material, usually of low toxicity, enhances the expression of toxicity by another. The result is a more severe injury than is produced by exposure to the toxic species alone. An example would be the enhanced central nervous system depression of carbon tetrachloride in the presence of alcohol. Parts per million. An expression of concentration as the number of parts of a contaminant in a million parts of air. Usually used for gases or vapours. If the TLV Booklet gives a skin notation for a chemical, it means that there can be a significant exposure due to skin, eye, or mucous membrane contact with the vapours, liquids or solids. Two materials act together to produce toxicity greater than that produced by either material if administered separately Threshold Limit Values – Workplace exposure guidelines. Short term (15 min) exposure limit Average exposure limit for an eight hour workday
3
TLV-C Toxicology
A ceiling exposure limit that should not be exceeded even for a short time. The science and study of chemicals and their adverse systemic effects, including source, chemical composition, action, tests, and antidotes.
4
Introduction to the guideline What Are Our Responsibilities For Workers’ Health?
General Duties The general duty to protect workers is spelled out in the Workplace Safety and Health Act 1. Under this act it is the responsibility of the employer to ensure the safety, health and welfare of all workers. This responsibility must be done to the extent that it is reasonably practicable. One of these responsibilities is the requirement to ensure that workers are not exposed to chemical substances that may cause adverse health effects.
Exposure To Chemical Substances The steps that must be taken to ensure the safety, health and welfare of workers resulting from the use, production, storage, handling, and disposal of chemical substances are spelled out in Part 36 of the Workplace Safety and Health Regulation, 217/2006. Part 36, Chemical and Biological Substances. A decision diagram of this regulation is shown in Figure 1. The part requiring that the exposure limits be adjusted to take into account conditions in your workplace (Section 36.5(2)) is circled. This section states that when: (a) conditions in the workplace, (including, heat, ultraviolet and ionizing radiation, humidity, pressure, length of work shift, work-rest regime, or additive and synergistic effects of materials and workload); or (b) the health or physical condition of a worker in the workplace known to an employer; the employer must establish a lower occupational exposure limit for that substance than the limit established by the ACGIH. The occupational exposure limit established by the employer must ensure that the safety or health of workers who are exposed to the substance in that workplace at levels below that limit will not be placed at risk.
We are now going to explore how to establish lower occupational exposure limits to protect all workers. 1
http://www.safemanitoba.com
5
Figure 1: Decision diagram for Part 36 of the Workplace Safety and Health Regulation, Chemical and Biological Substances. The circle shows the area to be addressed here.
6
What Are Occupational Exposure Limits And Why Must They Be Adjusted? Exposure limits are established concentrations which, if not exceeded, will not generally cause adverse effects to the exposed worker. Exposure levels were developed as guidelines or recommendations in the control of potential health hazards and are not fine lines between safe and unsafe exposures, nor are they a relative index of toxicity. The most commonly used workplace exposure limits are the Threshold Limit Values (TLVs®), guidelines proposed by the American Conference of Governmental Industrial Hygienists (ACGIH®). The TLVs are used in Manitoba as exposure limits. Part of the reason for the TLVs being guidelines is the variation in worker’s reactions to the same exposures, and the differences in working conditions. Since a guideline that is to be applied to many workers and workplaces cannot take into account all possible combinations of workers and workplaces, a model workplace was used that will cover most workers and workplaces. Essentially this can be thought of as a young healthy male worker, working 8 hours/day at an even exposure at a moderate exertion of energy. If your workplace is different from this standard workplace, then you must review the exposure limits to determine if there is a possible problem. It has been our experience that when problems arise in the application of TLVs or other exposure standards, it is the result of 1 of 2 possible lapses. 1. Overestimation of the tolerance of the worker/workforce by not recognizing the implications of an atypical worker/workforce in terms of age, reproductive status, pre-existing medical condition, etc.; or 2. Underestimation of exposure by not considering all routes of exposure, additive effects with multiple chemicals, increased dose via inhalation during physical exertion, non-occupational exposures etc..
What Is The Purpose of This Guideline? This guideline is to assist workplaces to comply with the regulations, apply the TLVs as intended, and protect all workers from the ill effects of workplace chemicals. As described above, if the conditions of the workforce or workplace are not taken into account, there is an increased probability that you will underestimate the risk to workers. This guideline is intended to be a screening method to help workplaces in the decision process to determine if: there is not likely to be a problem;
7
there is a problem and action is needed; or expert help is needed. The guideline cannot always provide absolute answers. Where you believe there is a problem, fix it or carry out a detailed assessment and document your findings or get expert help. Remember, failure to assess is a violation of your duty as well as the regulations.
What Are The Principles Used In This Guideline? This guideline will take you through the main conditions that can affect the risk to workers. It will provide guidelines to assist you to determine: If there is a Class 1 condition where the probability that the conditions of the workforce or workplace are not likely to have an unexpected effect on workers, and good health and safety practice will protect workers. If there is a Class 2 condition where the conditions of the workforce or workplace can affect some or all workers and rules of thumb to adjust the TLVs are given. If there is a Class 3 condition where the need to adjust the exposure level or the amount of adjustment is not clear, is complex, or requires confidential medical information and therefore expert advice is recommended.
8
ADJUSTMENTS FOR CONDITIONS OF THE WORKER ADJUSTMENTS FOR AGE ADJUSTMENTS FOR HEALTH ADJUSTMENTS FOR SEXUAL DIFFERENCES ADJUSTMENTS FOR PREGNANT WORKERS ADJUSTMENTS FOR SENSITIZATION ADJUSTMENTS FOR NONOCCUPATIONAL EXPOSURES
9
INTRODUCTION - WORKER There is a large variation in how different workers react to similar exposures in the workplace. These variations depend on many things such as genetics, age, health, reproductive status. If everyone reacted the same to the same chemical exposure, fixed standards could be used. Since this is not the case, you must adjust the TLV to accommodate individual workers. Failure to do this frequently results in an overestimation of a worker’s tolerance to workplace chemicals. This is the same as underestimating the risk to a worker. This could result in workplace related illness. The following is a description of the Classes of adjustments possible for conditions of the worker. See the following sections for details. Class #1 – There is not likely to be a significant impact on workers under these conditions. And good workplace practice should protect all workers. Class #2 – Under these conditions additional precautions as described should be implemented. Because we are often dealing with an individual health condition, there is often little we can do without the assistance of a physician. Class #3 – Under these conditions expert advice should be found. Since worker health condition is often the basis for the potential problem, the expert should be an occupational health physician or in some cases an occupational hygienist familiar with the toxicology of the materials used in your workplace. It is believed that the advice offered here will usually be conservative and offer more protection than is actually needed. For a more precise risk assessment, the help of a professional such as an occupational hygienist is needed.
10
CAUTIONARY NOTES Estimating Exposure Level In some cases, such as with older workers or with workers with health related issues, it necessary to know what their exposure to toxic workplace materials is as part of the risk assessment and adjustment process. Usually, if the exposure level is 10% and there are technical issues related to reducing exposure levels.
If TLVs were considered in setting the exposure limit, no change is required for normal healthy workers. Use good industrial hygiene practice and general ventilation. Adjust the TLV down by 30%
Expert advice to review the toxic properties of the chemical to determine if the TLV does in fact protect pregnant workers. If there is no recommendation for pregnant workers, expert advice should be found to develop an exposure limit for pregnant workers.
NOTE #1 Examples of materials where the TLVs took into account reproductive effects and adjustments do not have to be made. Acrylic Acid Carbon monoxide
Amitrole Chloroform
Carbaryl 2-Chloropropionic Acid
Dibutyl Phthalate Epichlorhydrin Ethyl Chloride Hexafluoroacetone Lead Arsenate
N,N-Dimethyl Acetamide 2-Ethoxyethanol Ethylene Oxide Indium & Compounds Lead Chromate
Mercury (Inorganic) Methyl tert-Butyl Ether Phenyl Glycidyl Ether Toluene
2-Methoxyethanol Methyl Chloride Phenylphosphine 4-Vinyl Cyclohexene
Dinitrotoluene 2-Ethoxyethyl Acetate Halothane Lead Manganese, Elemental & Inorganic Compounds 2-Methoxyethyl Acetate Nitrous Oxide Tin, Organic Compounds Vinyl Cyclohexene Dioxide
20
NOTE #2 Examples of TLVs where the exposure guideline was set on other effects but were believed to be low enough to take into account reproductive effects and adjustments do not have to be made. Acrylonitrile Carbon Disulfide Ethyl Benzene
Benomyl b-Chloroprene Ethylene Dibromide
Carbofuran Endosulfan Ethylene Glycol
Glycerin Mist Lithium Hydride Nitromethane Trichloroethylene
Hexachlorobenzene Mercury (Aryl Compounds) Parathion Warfarin
Hexamethyl Phosphoramide Methyl n-Butyl Ketone Sodium Fluoroacetate
NOTE #3 The Documentation ® contains much information about chemicals and how they affect the body. These should be reviewed to help determine if changes in the exposure limit is necessary. This would require the expert advice of a doctor or occupational hygienist.
NOTE #4 Although not a normal part of the workforce, there is a requirement to protect nursing infants. They should be protected either as part of the requirement to provide a safe workplace for mothers who breast feed or to ensure that persons who are not employed at the workplace are not exposed to risks arising out of that workplace.
EXAMPLE 1 A pregnant worker uses toluene, ethyl benzene and chlorobenzene. What adjustments should be made? A
Toluene – The TLV was set to protect pregnant workers (See Note #1) Ethyl benzene – The Documentation® shows that the TLV was set for effects other than pregnancy but was low enough to protect pregnant workers (See Note #2) Chlorobenzene – There was no readily available information so reduce the TLV by 30%. However, if an expert was called, they would have found, in the Documentation® Summary for chlorobenzene that the TLV is based on slight liver changes, including increased weight and congestion, reported
21
for rats exposed by inhalation to 50 or 75 ppm chlorobenzene. In the Reproductive/Developmental section it stated that rats exposed by inhalation at either, 0, 50, 150, or 450 ppm for two generations showed no adverse reproductive effects. This would suggest that reproductive effects occur at levels above the TLV and that adjustments are not required.
22
ADJUSTMENTS FOR SENSITIZATION Could you have a problem? What are the exposure levels in the workplace? What chemicals are you exposed to? Review Material Safety data Sheets. What symptoms can the chemicals produce? Review the TLV Booklet for a summary of systems affected. Review the Documentation for details. Review other sources to determine what illnesses the chemical can produce. Can the materials in question produce sensitization. Most chemicals do not produce sensitization. Estimate exposure levels by sampling to determine how much is in the air and how big a dose the worker is getting. Are there opportunities for exposures above the TLV since peak levels are more important to developing sensitization than are long term low level exposures? Even if the exposures are low (